Cat depression?

Yesterday we got rid of our kitten. And today her brother is acting very weird. Whats wrong with him and what should I do

Answer by KateIt is normal for a cat to miss or grieve for another cat. All you can do is make sure that they have plenty to keep them occupied and distracted. So lots of toys of different types and lots of time with you, games etc.

https://www.our-happy-cat.com/cat-toys.html

It may take a while for them to get over the fact that they may be wondering where the other cat is, but they will eventually, with your help and TLC.